A Lissajous curve, that can be expressed in parametric form as:

${\displaystyle x=A\sin(at+\delta ),\quad y=B\sin(bt)}$

with ${\displaystyle a=9}$, ${\displaystyle b=8}$ and ${\displaystyle \delta =\pi /2}$. I created it with the following GNUplot code:

set samples 5000 set terminal svg set output "Lissajous_curve_9by8.svg"  # plotting within a square set size square  # remove most of information from the picture set noxtic set noytic set key off  # plot set parametric a=9 b=8 delta=pi/2 plot [0:2*pi] sin(a*t + delta),sin(b*t) with lines linewidth 2